metamorphic
Red Quartzite / River Cobble
Quartzite (SiO2 with iron oxide impurities)
Hardness: 7 (Mohs scale), Color: Pinkish-red to maroon with grey veining, Luster: Vitreous to dull, Crystal Structure: Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Pinkish-red to maroon with grey veining, Luster: Vitreous to dull, Crystal Structure: Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific rounded specimen has been weathered and shaped by water transport (alluvial process) in a river or glacial environment over thousands of years.
Uses & applications
Used as decorative landscaping stone, crushed aggregate for road construction, and occasionally for lapidary work like tumbled stones or cabochons due to its durability.
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges from which it originated. It is frequently more resistant to chemical weathering than the marble it can sometimes be confused with physically.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its grainy, sandpaper-like texture beneath a smooth water-worn surface. Commonly found in riverbeds and glacial tills globally. Collectors look for unique vein patterns or intense coloration.
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